Using dated molecular phylogenies to help reconstruct geological, climatic, and biological history: Examples from Colombia

Attempts at historical reconstruction are based on limited data. We are more likely to produce accurate historical reconstructions by utilizing information from diverse sources and pooling data within the relevant research communities which will allow us to build up a moving picture of the geological, climatic, and biological evolution of our planet. We suggest that dated phylogenies of plants can contribute greatly to a better understanding of Earth history. Timing of phylogenetic splits of lowland restricted lineages on either side of the Andes could provide information on the timing of montane uplift and associated climatic changes. The timing of the arrival and diversification of organisms restricted to specific climatic regimes at a particular altitude can provide information on the age at which mountains reached a height adequate for that climate once corrected for global climate changes. As a model for study, we discuss how dated phylogenies in biome rich Colombia may contribute to an understanding of geological and climatic change in north-western South America. Lowland wet forest restricted lineages separated from the mid-Miocene, whereas lineages primarily restricted to mid-altitude cloud forests began to diversify from the mid- to late-Miocene and the majority of high-altitude Páramo lineages began to diversify during the Pliocene. The age of diversification of altitudinally restricted lineages therefore gives an indication of the age at which particular altitudes may have been reached.

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The evaluation of soil stability in loess hilly and gully region of Northern Shaanxi based on GIS

Based on the previous research in loess hilly region of Northern Shaanxi, this paper takes the soil erosion degree as the main measure of soil stability and the soil utility, annual average rainfall in flood season (from June to September), and topography, as the main measure indexes of soil stability. After that, the evaluation system of soil stability in loess hilly region of Northern Shaanxi can be constructed, which can be done by special analysis of GIS. The results illustrate that the soil stability showed a trend of high south-east and low north-west. Soil with good stability is mainly distributed in Ganquan County, and Yanchuan County, where vegetation coverage is high, vegetation types are mostly forest land and grassland, ecological environment is good, and precipitation erosion effect is not significant. Soil with intermediate stability is mainly distributed in Baota district and its surrounding areas, where the main vegetation types are bush fallow and grassland, and the terrain is flat and gently rolling. Soil with the worst stability is mainly distributed in Suide County, and Wuqi County. The area is mostly sandy and desert, the terrain is fragmented, soil is loose, vegetation cover is not high, making the soil the worst soil stability, and strong rainfall conditions are prone to soil erosion. The prerequisite of the implementation of soil consolidation projects is having evaluation on soil stability. The research results can be the theoretical evidence, and implement guarantee of regional soil exploitation and reorganization, and the reference to enhancing the assurance of ecological safety.

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3D imaging of the crust and upper mantle beneath the Arctic Ocean from Rayleigh-wave group-velocity analysis

A 3D S-velocity model for the crust and upper mantle beneath the Arctic Ocean is determined from the analysis of fundamental-mode Rayleigh-wave group velocity. This new model allows the characterization of the principal features present beneath the Arctic Ocean, in terms of S-velocity, for a depth range from 0 to 400 km. In the depth range from 0 to 5 km, the basins with thicker sediments are imaged by the lowest S-velocity values (2.2–2.3 km/s), whereas the highest S-velocity values (3.2–3.3 km/s) are associated with a thin sedimentary cover. In the depth range from 5 to 10 km, the lowest S-velocity values (2.6–2.7 km/s) are also shown in areas with a thick sedimentary cover (>10 km). The higher S-velocity values (4.0–4.2 km/s) are associated with the areas in which the Moho depth is overcome. In the depth range from 10 to 35 km, also the S-velocity values are higher (>4 km/s) for the zones in which the Moho depth is overcome. The S-velocities determined in this study allows to consider the Alpha-Mendeleev Ridge (formed by the Alpha Ridge and the Mendeleev Ridge) as a continuous feature, because the Alpha Ridge and the Mendeleev Ridge are characterized by similar S-velocities (e.g., ~3.6 km/s for depths from 10 to 15 km). This region also can be considered as an oceanic large igneous province, in terms of S-velocity, because the determined S-velocity pattern is characteristic of these oceanic regions. In general, for the lithosphere (from 35 to 180 km depth), the S-velocity can be easily correlated with the different age of the Arctic Ocean regions and with the surface tectonic features, whereas for the asthenosphere and the mantle below it (from 180 to 400 km depth), this correlation is not clear. In general, a small S-velocity contrast (0.1–0.2 km/s) is found between the lithosphere and asthenosphere, which makes it difficult to determine this boundary. Opposite to this, the high S-velocity contrast (0.4–0.5 km/s) found at the asthenosphere base allows the easy determination of this boundary.

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Controls of a Triassic fan-delta system, Junggar Basin, NW China

Both sedimentology and sequence stratigraphy variability in the deltaic area are distinguished in the fan-delta system of the Northwestern Junggar Basin. Sediment supply plays a significant role in controlling the fan-delta petrology, evolution, and depositional processes and the delivery of sediment into deeper parts of the basin. The results of this study show that variations in the lithology of the sediment supply control the fan-delta petrology and spatial and temporal variations in sediment supply influence the location and shifting of depocentres. A fining-upward fan-delta succession developed as accommodation rates outpaced the sediment supply rate. Frequent flood events were mostly recorded by sediment gravity flow deposits, which in turn influenced the geometry of the sandstone bodies and their reservoir quality. Hyperpycnal flow was a significant delta front process and an important mechanism for sediment delivery into deeper waters, favoured by the combination of denudation of coastal ranges and the fresh waters of the receiving basin. This study highlights that a detailed understanding of variations in sediment supply is essential to accurately predict sediment partitions in a delta system and the delivery of coarse-grained sediments into deeper parts of lacustrine basins.

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Geochemical characteristics of Late Carboniferous volcanic rocks in South-eastern Heishanling, Beishan area, Xinjiang, China

The Palaeozoic Beishan Rift Valley zone in Xinjiang, China, is located between the Dunhuang and Kuluketage blocks, in the north-eastern margin of the Tarim Plate. Carboniferous–Permian volcanism is evident in this area. The Ganquan cycle, the main eruptive event of the Late Carboniferous in the Beishan region, produced large volumes of lava and was related to Carboniferous–Permian volcanism in the rift valley. Major element, rare earth element (REE), and trace element compositions of volcanic rocks were determined, with results indicating that volcanic rocks of the Ganquan cycle are mainly an association of sodic calc-alkaline rocks, with some alkaline compositions. The REE characteristics of all rock types indicate a continuous and progressive evolution, with a gradual increase in light REE enrichment, and positive to negative Eu anomalies reflecting crystallization of plagioclase. Trace element compositions show obvious depletion in Nb and Ta, and high abundances of large-ion lithophile elements, indicative of a subduction-related origin. It is concluded that the Late Carboniferous Beishan Rift Valley of the Ganquan cycle formed in a compressional tectonic environment, which generated a set of volcanic rock assemblages and sedimentary formations. Subsequent Early Permian volcanic activity was caused by large-scale delamination of the orogenic belt and thickened lithosphere, which resulted in large-scale ascent of partial melt from the mantle.

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Depositional processes and sedimentation pattern in an intermontane basin: Insights from the Imphal Basin, Indo-Myanmar Range, NE India

Intermontane basins make a distinct category of sedimentary basins, but nevertheless, the depositional processes and sedimentation patterns therein are not well understood. Quaternary sediment-filled Imphal Basin in the Indo-Myanmar Range provides us with an excellent opportunity of lending insight into these sedimentological aspects of an intermontane basin. Detailed facies analysis brings out that five distinct facies associations (“FAA”–“FAE”) have developed in different parts of the basin, each one of which indicates a specific subenvironment of deposition. Facies characters and spatial distribution of facies associations reveal that the basin fill records interlinked lacustrine, fluvial, and alluvial fan processes. Comprising mud and peat, the facies association “FAA” represents deposits of a lake and lakeshore swamp. The facies association “FAB” comprises mud interfingered with crudely bedded gravel and represents suspension fallout in a lake with intervening gravel-rich, hyperconcentrated flows that diffusively plunged into the lakebed. The sand-dominated facies association “FAC” and gravel-dominated facies association “FAD” were deposited in fluvial domains of meandering and braided streams, respectively. Rimming the basin margin, the gravel-dominated facies association “FAE” was deposited in the alluvial fan–interfan areas. Widespread development of the lacustrine facies (“FAA” and “FAB”) around the Loktak Lake along with extensive peat development over the lacustrine mud suggests lakeshore regression and development of vast swamps under humid conditions. The regression under humid conditions could be a result of fast and enhanced influx of finer sediments into the lake that transcended the creation of accommodation space and ultimately led to faster infilling of the lake margins favouring development of vast swamps in due course of time.

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The Central Canyon depositional patterns and filling process in east of Lingshui Depression, Qiongdongnan Basin northern South China Sea

Central canyons are considered to be important conduits for the transfer of sediment to the abyssal plains. High-resolution 3D seismic data and logging data from the east of Lingshui Depression are used to investigate the depositional elements, patterns, and filling processes of central canyon in the Qiongdongnan Basin, northern South China Sea. The Central Canyon in this segment is 30 km wide and more than 1,000 m deep. It was found to be characterized by being subparallel to the continental shelf. In this study, 6 types of deep-water gravity flow depositional elements were identified, including erosion surfaces, basal lags, turbidite channel complexes, mass transport deposits, lobe complex, and pelagic deposits. Each type of these depositional elements was found to have distinct external features, internal structures, and lateral characteristics in the seismic profiles. Meanwhile, these different assemblages of depositional elements could be composed of 5 depositional units. And in a vertical direction, the evolutionary history could be divided into 5 stages as follows: (a) a repeated cut and fill stage; (b) high net-to-gross channel complex dominated stage; (c) low high net-to-gross channel and pelagic shale dominated stage; (d) lobe complex deposition stage; and (e) mass transport deposit dominated stage. During Stage 3, the development of small-scale turbidite channels is the indicators of northern sediment supply. During Stage 4, 7 lobes have been identified in the lobe complexes. The evolution and depositional processes in the study area were most likely controlled by the negative relief induced by the palaeo-seafloor morphology, as well as the structural inversions of the Red River Fault and the basement faults. Additionally, the sediment supply, sea-level fluctuations, and tectonic activities also controlled and influenced the depositional processes, along with the internal architecture of the canyon.
The results of this study have potentially important implications for the improved understanding the vertical evolution of submarine canyons and also shed a new light on the reservoir potential of the Lingshui section of the Central Canyon.

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Mkango Receives £6 Million (C$10.5 Million) Investment From Talaxis And Commences Feasibility Study For The Songwe Hill Rare Earths Project In Malawi

London / Calgary: January 24, 2018 – Mkango Resources Ltd. (AIM/TSX-V: MKA) (the \’Company\’ or \’Mkango\’) is pleased to announce that following receipt of both shareholder and final TSX Venture Exchange approval, investments totalling £6 million (C$10.5 million) have been received by Mkango subsidiaries in accordance with the previously announced agreement (\’Agreement\’) with Talaxis Limited (\’Talaxis\’):

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